The electrophotographic image forming device is a device for forming an image on a recording material by electrophotographic imaging processing, for example, an electrophotographic copier, an electrophotographic printer (a laser printer, an LED printer, etc.), a facsimile apparatus, a word processor and the like.
FIG. 1 is a schematic diagram illustrating the engagement of the traditional process cartridge and image forming device. The traditional image forming device comprises a main frame 1 for the image forming device and a process cartridge 10 slideably coupled to the main frame 1, wherein the process cartridge 10 comprises components (not shown in the figure) among a developer, a developing roller, a supply roller, a doctor blade, a photosensitive drum and the like, and a photosensitive drum driving gear 15 engaged with a main frame driving gear 5 for transmitting driving force; first lugs 11 coaxially arranged with the photosensitive drum and second lugs 12 positioned at the downstream side of the first lugs 11, relative to the installation direction of the process cartridge, are formed on the surfaces of the opposite end parts of both sides of the process cartridge; the first lugs 11 and the second lugs 12 on the end parts of both sides of the process cartridge 10 are slideably coupled to the main frame 1 along curved guide rails 2 on two sidewalls of the main frame 1; the guide rails 2 guide the process cartridge 10 to enter into first lug installation positions 2a and second lug installation positions 2b; the shape of the guide rails 2 is as shown in FIG. 2; and tail ends 2c of the guide rails 2 are horizontal. When the first lugs of the process cartridge 10 are positioned at the installation positions 2a at the tail ends 2c of the guide rails 2, the first lugs 11 of the process cartridge 10, at the axial direction of the photosensitive drum, is under the action of the elastic pressure of stop components (such as springs, not shown in the figure), so that the process cartridge 10 is accurately positioned. Meanwhile, the photosensitive drum driving gear 15 of the process cartridge 10 is engaged with the main frame driving gear 5 on the main frame 1 for the image forming device, when the process cartridge 10 is assembled into the main frame.
The force condition of the process cartridge 10 when the image forming device is in the operating state is as shown in FIG. 2. When the process cartridge 10 is in the operating state, the photosensitive drum driving gear 15 of the process cartridge is engaged with the main frame driving gear 5; gear driving force F is transmitted from the main frame driving gear 5 to the process cartridge 10; the photosensitive drum driving gear 15 of the process cartridge is under the action of tangential force Ft along the tangential direction of the photosensitive drum driving gear 15 and radial force Fn along the direction of a line that links centers of the photosensitive drum driving gear 15 and the main frame driving gear 5, which are resolved by the gear driving force F; the tangential force Ft drives the photosensitive drum gear 15 to rotate; and the radial force Fn pushes the process cartridge 10 off an installation position. Therefore, elastic forcible pushing components (such as springs, not shown in the figure) are usually required to be arranged at the installation positions 2a of the first lugs 11, coaxially arranged with the photosensitive drum of the process cartridge, so that the process cartridge 10 is prevented from being disengaged. As the elastic forcible pushing components are required to be able to prevent the process cartridge 10 from being disengaged from the guide rails 2 and prevent the process cartridge 10 from rotating, the component, namely the radial force Fn, of the gear driving force F can be resolved into a horizontal component Fnx and a vertical component Fny in the horizontal direction and the vertical direction respectively, as shown in FIG. 2. By adoption of the shape design, the guide rails of the traditional image forming device can only restrain the vertical component Fny of the radial force Fn and cannot restrain the horizontal component Fnx of the radial force Fn, so the elastic forcible pushing components (such as the springs) are required for preventing the process cartridge from being disengaged from the guide rails. However, the position bears large thrust force; the performance requirement of the springs is relatively high; and the positioning accuracy of the process cartridge in the image forming device is affected. Moreover, although the engagement mode of the traditional image forming device and process cartridge is simple, the process cartridge 10 can be driven to be disengaged from the installation position when the photosensitive drum driving gear 15 of the process cartridge 10 is under the action of the driving force of the main frame driving gear 5 of the image forming device, and consequently the image quality is poor.